1. Field of the Invention
The present invention relates to a transfer device centering method in a system including various kinds of processing units for performing various kinds of processing for a substrate such as a semiconductor wafer or the like and a transfer device for transferring the substrate between these processing units, and a substrate processing apparatus.
2. Description of the Related Art
In a coating and developing system in processes of semiconductor device fabrication, for example, a semiconductor wafer (hereinafter referred to as a wafer) is coated with a photoresist solution, and by means of photolithography, a circuit pattern or the like is produced and a photoresist film is exposed and developed.
The coating and developing system has a structure in which a cassette station into which a cassette housing wafers is carried and out of which the wafers are carried one by one, a processing station in which various kinds of processing units for performing various kinds of processing for coating and developing for the wafer are multi-tiered, and an interface section for transferring the wafer between an aligner provided adjacent to the processing station for exposing the wafer and the processing station are integrally connected.
In the above coating and developing system, in the cassette station, the wafers are taken out of the cassette and transferred to the processing station one by one. After being cleaned in a cleaning unit, the wafer undergoes hydrophobic processing in an adhesion unit, and it is cooled in a cooling unit and then coated with a photoresist film in a resist coating unit. Thereafter, the wafer undergoes baking processing by being heated in a baking unit.
Subsequently, the wafer is transferred from the processing station to the aligner via the interface section, and a predetermined pattern is exposed in the aligner. After being exposed, the wafer is transferred again to the processing station via the interface section. The exposed wafer undergoes baking processing (post-bake) after a developing solution is applied to thereby form the predetermined pattern in a developing unit. After a series of processing described above is completed, the wafer is transferred to the cassette station and is housed in the wafer cassette.
Incidentally, in the aforesaid series of coating and developing processing, a wafer transfer device for transferring the wafer between a plurality of processing units for performing various kinds of processing such as cleaning processing, coating processing, developing processing, baking processing, and the like is provided to be movable vertically in the processing station.
The wafer transfer device has tweezers movable horizontally, and the wafer transfer device itself is ascendable and descendable vertically (in a Z-direction) and rotatable in a .theta.-direction. Thus, the wafer transfer device receives and sends the wafer from/to each processing unit with the tweezers, and the wafer transfer device itself ascends and descends vertically (in the Z-direction) and rotates in the .theta.-direction to thereby get access to various processing units.
It is required to carry out centering for adjusting the position of tweezers in predetermined timing so that the wafer is accurately mounted on a mounting table when the wafer transfer device delivers the wafer to the mounting table in each of various processing units while the wafer is mounted on the tweezers. Namely, it is necessary to adjust a position at which the tweezers finally delivers the wafer to the mounting table after moving while the wafer is mounted thereon.
Aforesaid centering of the wafer transfer device is performed for each processing unit at the time of initialization of the coating and developing system, and also in other cases, centering of the transfer device is regularly or irregularly performed. There is, however, a demand that the aforesaid centering be performed automatically without spending much time.